These Standard Chair Pads are high-quality, durable and professional-grade sensor pads. Each chair pad is categorized based on expected lifetime, and in general, the thicker the film the longer it will last. Those pads with a silver lining are also shown to last longer than those without. The 45-Day Pad is .05mm thick with carbon-lined conductive film, the 180-Day pad is .1mm thick with carbon and silver-lined conductive film, and the 1-Year Pad is .11mm thick, with silver-lined conductive film.